Single-use biocontainers 10 as shown in FIG. 1 are manufactured for use in conjunction with hardware designed around a platform 12 that oscillates in a rocking or seesaw motion, as for example described in U.S. Pat. Nos. 6,190,913, 6,544,788 and 7,195,394, the contents of which are fully incorporated herein by reference. This rocking motion, typically on the order of 12 to 20 degrees total sweep at a rate of 4-25 cycles per minute, is transferred to the biocontainer about an axis 14 which in turn imparts motion to a fluid and/or gas contained therein. For convenience the term “fluid” as used hereafter after refers to a fluid, or a gas, or to the combination of a fluid and, a gas. The imparted fluid motion is often used to accomplish unit processing steps within the biopharmaceutical industry, e.g. mixing or cell culture operations. The latter of these examples can require extended processing times on the order of one week to three months plus during which the oscillatory rocking motion is repeated constantly. These extended operating periods subject the biocontainer to high cyclical stress loads which can lead to breaches in the fluid containment area.
The biocontainers manufactured for use in conjunction with the aforementioned rocking platforms are typically single-use bags of construction such as shown in FIG. 2A. It should be noted that “bag(s),” “biocontainer(s)” and “biocontainer bag(s)” are used interchangeably herein. Representative biocontainers are two-dimensional in nature and are manufactured from two sheets (films) 16A, 16B of polymeric film 16 having dimensions (H1×W1) that are welded together along weld lines 18, 20, 22, 24, 26 and 28 to create a contained seal geometry. The welds along the weld lines form seams. Thus, the terms “weld lines” and “seams” are used interchangeably herein to refer to the area of bonding between the two sheets of polymeric film. These biocontainers contain porting 29, for fluid ingress and egress as well as gas exchange, which are welded within a fluid containment area 16 (H2×W2) defined between weld lines 18, 20, 22 and 24. The weld lines form seams. Additionally, the biocontainers include rigid support rods 32 at each end which are sealed into segregated areas 33 of the biocontainer (H3×W3) defined between weld lines 20, 26, 18 and 22, and 24, 26, 18 and 22, respectively. The support rods are used to help secure the biocontainer to the rocking platform. The rocking platform includes at least two clamps, such that each clamp clamps on the segregated areas and specifically the rod in such areas for securing each end of the biocontainer in place.
When the biocontainers are deployed, i.e. secured to the rocking platform and filled to capacity with a fluid, three distinct zones 34, 36 and 38 form. A first zone 34 also referred to herein as “Zone 1” is a two-dimensional zone in that it remains relatively flat. This area of the flexible single-use biocontainer is constrained by the rocking platform clamp and thus retains it two-dimensional “flat” shape. A second zone 36 referred to herein as “Zone 2” is a transitional zone. In this area, the biocontainer shape transitions between a generally two-dimensional shape at one end and the fully developed three-dimensional shape at its other end. A third zone 38 also referred to herein as “Zone 3” is a three-dimensional zone. In this zone, the biocontainer has developed its three-dimensional shape and has a cross-sectional shape along its length which is oval as a result of the fluid fill volume.
With the current biocontainers depicted in FIG. 2A, folding, crumpling and/or other undesirable film shapes can occur in Zone 2, i.e., in the transitional zone, due to geometry constraints associated with the transition between the two-dimensional end portion and the three-dimensional center portion. These undesirable film shapes create stress concentrations which when combined with the cyclical stress associated with the oscillatory motion of the fluid within the biocontainer, serve to decrease the service life of the biocontainer. Premature failures are believed to be due to either, a stress crack in the polymeric film material at a stress concentration point, or abrasion between the two films at a contact point. Both of these failure mechanisms manifest themselves in a repeatable nature in the four identified areas D in the transitional zones 36 of the current biocontainers and are directly attributable to the aforementioned undesirable film shapes in the transitional zones (Zones 2).